Estuaries occur where rivers and streams meet the sea. They are highly productive ecosystems that provide critical habitat for a diversity of species. The importance of estuaries as nursery habitat for juvenile salmon is well documented - providing abundant food resources, refuge from predation, and a physiological transition zone as young fishes move from fresh to salt water (Simenstad et al. 1982). In addition to their benefits to wildlife, estuaries offer people recreational, cultural, economic, and regulating services.

Over the last 150 years, the region has suffered dramatic losses of tidal wetlands (Simenstad et al. 2012, Brophy et al. 2019). These losses can largely be attributed to agricultural and industrial development (Collins and Sheikh 2005). Estuaries and tidal wetlands provided an opportunity to develop flat land near water, and were diked, drained, and in some cases filled. Diking and drainage allowed for development of farms on rich fertile marsh soils. Dredging and filling enabled the construction of modern ports and industrial sites. Loss of intertidal wetlands has contributed to the decline of many species, especially Chinook and chum salmon that depend on river delta estuaries for rearing habitat.

• Puget Sound contains 16 large river deltas, covering approximately 100,200 acres. Within these boundaries, 76,500 acres are mapped as current or potential tidal wetland habitat (excludes areas that are developed or outside of tidal extent). 28 percent of the wetland habitat has unrestricted tidal connectivity (all surrounding and downstream wetlands are open to tidal flooding). Nine percent of the wetland area is tidally influenced habitat, but connectivity is either partially or significantly restricted. 61 percent of Puget Sound’s delta wetland area has been completely blocked from tidal connectivity.
• Tidal restrictions, such as dikes/levees, roads, railways, and armored banks, restrict or prohibit tidal connectivity and wetland function. Cramer Fish Sciences mapped over 760 miles of restrictions that completely block tidal connectivity in Puget Sound’s large river deltas. This includes approximately 455 miles of roads and railways, 220 miles of dikes/levees, and 87 miles of armored banks.
• Removing tidal restrictions and improving the connectivity of tidal restriction features represent the best opportunities to increase functional and accessible tidal wetland habitat in Puget Sound.
• Since 2006, restoration activities have reintroduced or improved tidal connectivity to 3,420 acres in Puget Sound’s large river deltas. Most restoration occurred in the Snohomish, Nisqually, Skagit, Stillaguamish, and Skokomish deltas.
• A change analysis comparing tidal wetland connectivity between 2011 and 2020, showed gains in estuary function from restoration. The analysis did not identify any wetland loss or new restrictions to tidal connectivity over the 10-year period. While this points to improving progress in estuary function, extensive areas of historical habitat remain lost or degraded in many Puget Sound deltas.
• The extent and composition of functional estuary area varies by Puget Sound delta. Please see the Interpretation of Results section for more detailed summaries.

The extent and composition of functional estuary area in Puget Sound’s large river deltas varies by geographic region. The river deltas of the Strait of Juan de Fuca and Hood Canal originate in the northern and eastern Olympic Mountains and enter Puget Sound as steep, narrow estuaries (Collins and Sheikh 2005). Subsequently, the surface area of these river deltas is much less than that of the broad, low gradient deltas draining the Cascade Range. The Skagit and Snohomish estuaries are uniquely large. Together, these deltas represent nearly 60 percent of Puget Sound’s mapped geomorphic delta area and 50 percent of Puget Sound’s currently connected wetland area (including wetlands with unrestricted, partially, and significantly restricted tidal connection).

Mapped delta area (acres) for each category of tidal wetland connectivity under current (2020) conditions. Tidal connectivity is categorized as unrestricted (all surrounding and downstream wetlands are open to tidal flooding), partially restricted, significantly restricted, or completely restricted. Areas that have been developed, filled, or are outside of the tidal extent were excluded from tidal wetland mapping. In some cases, wetland connectivity could not be determined and is classified as unknown. Deltas are organized by Local Integrating Organizations (LIO) boundaries.

Cramer Fish Sciences Mapping Tidal Restrictions and Tidal Wetlands final report includes comprehensive summaries of restrictions and wetlands mapping by river delta and is available here. Estuary wetland habitat is summarized below by Local Integrating Organization (LIO) areas.

Strait of Juan de Fuca

The Elwha River delta is actively prograding due to recent dam removals, resulting in ongoing changes to delta area and habitat. The tidal wetland extent is mostly unrestricted with relatively few tidal restriction features present. In comparison, dikes/levees, roads, and bank armoring are prevalent in the Dungeness River delta. Most of the wetland habitat is classified as significantly or completely restricted except for the area around the mouth of the Dungeness River which is primarily unrestricted tidal wetland.

Hood Canal

The five Hood Canal river deltas (Dosewallips, Duckabush, Hamma Hamma, Quilcene, and Skokomish) are small in area relative to the other Puget Sound river deltas. While these deltas are small, they have 

remained largely intact and provide the Hood Canal region with an important source of estuarine wetland habitat. These deltas have little development and few features influencing tidal connectivity. Nearly all the wetland habitat is classified as having unrestricted tidal connectivity. Beginning in 2007, large-scale restoration efforts in the Skokomish removed dikes/levees and roads and restored unrestricted tidal connectivity to much of the delta’s wetland habitat.

South Sound

The South Sound region includes the Deschutes and Nisqually River deltas. The estuary extent in the Deschutes is largely confined to the main channel and Capitol Lake. Tidal connectivity in Capitol Lake is significantly restricted. Beginning in 2006, large-scale restoration efforts in the Nisqually removed dikes/levees and roads and restored unrestricted tidal connectivity to most of the delta’s wetland habitat.

Puyallup/White and South Central

Little wetland habitat remains in the two urbanized and industrialized deltas in South Central Puget Sound (Duwamish and Puyallup). Most of the area within these deltas is mapped as developed and filled. The tidally influenced area in both deltas is largely confined to the main distributary channel network, rather than small tidal channels and vegetated wetland. Consequently, most tidal wetland habitat is classified as unrestricted.

Both the Puyallup and Duwamish deltas have experienced the greatest proportional loss of historic tidal wetlands, and very little off-channel habitat remains (Simenstad et al. 2011). While in moderately altered systems there are opportunities to restore tidal flow that has been blocked, in these urbanized deltas, nearshore fill and development severely limits the extent of potential estuary suitable for restoration.

Snohomish/Stillaguamish

The Snohomish delta is the second largest of the Puget Sound river deltas and includes nearly 15,000 acres of wetland habitat. Over 10,000 acres in this delta are completely restricted from tidal inundation while nearly 3,000 acres are classified as unrestricted. Much of the restoration that has occurred since 2006 has been in the Snohomish (1,150 acres) and Stillaguamish (490 acres) deltas.

Skagit/Samish

The Skagit River has the largest delta footprint in Puget Sound and includes nearly 35,000 acres of wetland habitat. However, tidal connectivity in most of this wetland area (73%) is completely restricted. Still, the Skagit delta contains over 8,300 acres of unrestricted tidal wetland habitat, accounting for nearly 40% of the total unrestricted wetland habitat among Puget Sound’s large river deltas. In the Samish, extensive levees span the shoreline and riverbanks and prevent tidal connectivity to most of the delta.

Whatcom

The Nooksack delta includes two lobes for the Nooksack and Lummi rivers, with both being impacted by tidal restriction features. However, the Lummi River lobe is much more restricted as compared to the Nooksack River delta lobe. 20% of the delta footprint is mapped as developed or outside of tidal extent. The remaining wetland area is mostly classified as significantly or completely restricted. The Nooksack does have over 1,500 acres of unrestricted wetland habitat, primarily at the lower lobe of the Nooksack River that has been prograding since connectivity to the Lummi River distributary and lobe was reduced.

Change Analysis Results

A total of 1,484 wetland acres changed tidal connectivity classification between 2011 and 2020. Most of the wetland changes were due to restoration efforts that removed or breached tidal restrictions (1,465 acres). The exception is the Elwha River delta which is actively prograding due to recent dam removals. Cramer Fish Sciences updated the lower Elwha delta boundary in the 2020 dataset to incorporate newly formed tidal islands, mudflats, and channels. This growth is noted in the indicator change analysis. We did not identify any wetland loss or new tidal restrictions in our review of changes over the 10-year period.

The table below lists the connectivity changes we identified as occurring between 2011 and 2020. Restoration and other changes that may have occurred before this period are not summarized here.

Estuary Restoration

Puget Sound Partnership staff continue to compile data on estuary restoration projects for each year since 2006. In total, restoration activities have reintroduced or improved tidal connectivity to 3,420 acres in Puget Sound’s large river deltas. Restoration project footprints can be viewed in the indicator map.

The Estuaries Vital Sign previously had a recovery target for estuary restoration, expressed as: By 2020, all Chinook natal river deltas meet 10-year salmon recovery goals (or 10 percent of restoration need as proxy for river deltas lacking quantitative acreage goals in salmon recovery plans) and 7,380 quality acres are restored basin-wide, which is 20 percent of restoration need. The target was not met by 2020.

Puget Sound Large River Delta Tidal Restriction and Wetland Mapping - Salish Sea Wiki (salishsearestoration.org)

Floodplains and Estuaries Implementation Strategy - Strategic Initiatives of the Puget Sound National Estuary Program (wa.gov)

Estuary and Salmon Restoration Program | Washington Department of Fish & Wildlife

Collins, B.D. and A.J. Sheikh. 2005. Historical reconstruction, classification, and change analysis of Puget Sound tidal marshes. Prepared for Washington Department of Natural Resources. Puget Sound River History Project, Department of Earth and Space Sciences, University of Washington, Seattle, WA.

Czuba, J.A., C.S. Magirl, C.R. Czuba, E.E. Grossman, C.A. Curran, A.S. Gendaszek, and R.S. Dinicola. 2011. Sediment Load from Major Rivers into Puget Sound and its Adjacent Waters. USGS Fact Sheet 2011-3083.

Simenstad, C. A., K. L. Fresh, and E. O. Salo. 1982. The role of Puget Sound and Washington coastal estuaries in the life history of Pacific salmon: an unappreciated function. Pages 343-364 in Estuarine Comparisons.

Simenstad, C.A., M. Ramirez, J. Burke, M. Logsdon, H. Shipman, C. Tanner, J. Toft, B. Craig, C. Davis, J. Fung, P. Bloch, K. Fresh, S. Campbell, D. Myers, E. Iverson, A. Bailey, P. Schlenger, C. Kiblinger, P. Myre, W. Gerstel, and A. MacLennan. 2011. Historical Change of Puget Sound Shorelines: Puget Sound Nearshore Ecosystem Project Change Analysis. Puget Sound Nearshore Report No. 2011-01. Published by Washington Department of Fish and Wildlife, Olympia, Washington, and U.S. Army Corps of Engineers, Seattle, Washington.